1. Field of the Invention
The present invention relates generally to semiconductor wafer cleaning and preparation, and more particularly, to a method and apparatus for cleaning or preparing wafer edges after various fabrication operations.
2. Description of the Related Art
In the field of semiconductor chip fabrication processing, it is well known that there is a need to clean a semiconductor substrate wafer where a fabrication operation has been performed that leaves unwanted residuals on the surface of the wafer. Examples of such fabrication operations include plasma etching, material depositions and chemical mechanical planarization (CMP). CMP is commonly performed on both dielectric materials and conductive materials such as oxide and copper. If particles or films are left on the surface of the wafer without removing them, the unwanted residual particles or material may cause defects on the wafer surface and inappropriate interactions between metallization features or with subsequent lithography operations. Such defects may cause devices on the wafer to become inoperable. It is therefore necessary to clean the wafer after fabrication operations that leave unwanted residuals on the surface of the wafer.
A common fabrication operation includes the deposition of metals over previously formed dielectric features, which is commonly done in damascene and dual-damascene processes. As is generally defined, damascene and dual-damascene processes include the formation of features, such as interconnect lines and vias into dielectric materials, filling the dielectric features with conductive material, e.g., such as copper, and then performing CMP operations to remove the excess metallization material. The metal material can be formed over the wafer using various techniques, such as, for example, deposition, electroplating, sputtering, and the like. In either case, the formation of metal material may generate excess beading around the periphery of the wafer. It is also a common operation to perform standard cleaning operations after such metal deposition operations, to ensure that the excess material, debris, and contaminants are removed from the wafer before engaging in further processing.
Standard brush scrubbing techniques often fail to clean and remove the metal edge beading and loose particles from wafer edge surfaces including the bevel edge and exclusion zone which extends from about 1 to 3 millimeters from the bevel. Although sufficient center cleaning is performed using roller brushes, not enough mechanical scrubbing is performed at the edge. Consequently, unwanted material may remain even after repeated conventional brush cleaning.
FIG. 1 shows an exemplary prior art wafer brush-box 50. The brush-box 50 includes a drive roller 61 that rotates in a direction 62 that drives the wafer 12 in a direction 63, and a stator roller 68 that forces the wafer into engagement with the circumferential groove 70 of drive roller 61. Edge cleaner 65 cleans the bevel 74 of the wafer 12. Edge cleaner 65 may rotate in the direction 67 at a different speed than the drive roller 61 to provide some scrubbing action between edge cleaner 65 and wafer bevel 74. Edge cleaner 65 comprises a grooved roller having a soft compliant material lining the groove for conforming to the edge profile and removing debris. An exemplary edge cleaner of this type is shown in U.S. Pat. No. 6,334,229, which issued to Moinpour et al. on Jan. 1, 2002. Stationary, U-shaped scrub brush edge cleaners are also known.
Unfortunately, prior art wafer edge cleaners must be replaced periodically, increasing operating costs. Furthermore, the prior art devices have a small area of contact between the cleaning implement and the wafer. The small area of contact results in reduced efficiency in cleaning, requiring longer cleaning times.
In view of the foregoing, there exists an unmet need for a substrate edge cleaning system and method that provides a less costly, more effective and efficient alternative to current technologies.